Many osteo-articular diseases involve the degeneration of only one side of an articular joint such as chondromalacia, and avascular necrosis. In order to improve the parient's condition, this articular surface or articular defect may be replaced by an implant which functions as an artificial cartilage. Unfortunately, this articulation of an inert material with relatively healthy cartilage may cause problems on a long term basis, such as cartilage wear leading to the recurrence of pain. It is postulated that this surgical technique could be improved through providing an intrinsic boundary lubrication mechanism attached to the surface of the artificial material. The long term objective of the project is to determine if phosphatidylcholined (predominant phospholipids in synovial fluid) ionically attached to an elastomeric surface can be used to reduce friction and wear of cartilage in hemiarthroplasty conditions or for the repair of osteochondral defects. The specific aims of this study are: 1:To measure the coefficient of friction of articular cartilage bearing against a chemically treated elastomeric surface under simulated physiological conditions. 2:To characterize the role of phospholipid coating and its thickness in synovial joint lubrication for the contact cartilage/elastomer in vitro. 3:To develop a mathematical model of the elastic contact between cartilage, phospholipid layer, and elastomer to predict the behavior of the surfactant in biomechanical conditions. It is proposed to etch the surface of an elastomeric material to render it negatively charged. The bonding of a layer of phosphatidylcholine on this surface as a surfactant will reduce the coefficient of friction between elastomer and cartilage. An in vitro tribological study (simulating physiological conditions) of the contact elastomer-cartilage will enable the evaluation of the effect of surface treatment on the reduction of the coefficient of friction. These tests will be also performed with untreated elastomeric surface. Solutions of phospholipids and hyaluronic acid will be used as lubricants. Fatigue tests will be performed to characterize the adhesion of the phospholipidic coating onto the elastomer. After testing both cartilage and elastomer structure will be characterized.